The following piperazine compounds with insecticidal and fungicidal activity were known in early U.S. Pat. No. 3,394,137:
                R1 is selected from alkyl or haloalkyl        
The following piperazine compounds with insecticidal and fungicidal activity were known in patent JP2001354657:

Some piperazine compounds with insecticidal and fungicidal activity as agrochemicals were also known in patents, such as JP 2006188462, US 20080076777, CN101128445, US20050032810 and US20030207894.
Some piperazine compounds with pharmaceutical activity were disclosed in patents, such as CN1040029, CN1969853, JP2003335681, U.S. Pat. No. 2,993,062, U.S. Pat. No. 5,872,115, U.S. Pat. No. 6,313,127, US2005119251, US20070027118, US2007004750, US20070190079, US2007219198, WO9728128, WO02102778, WO2004002965, WO2004078732, WO2005023260, WO2006014168. WO2006094843, WO2007009635, WO2007066784, WO2007141039 etc. and references, such as Khimiyai Khimicheskaya Tekhnologiya (2004), 47(8), 91-96; Archiv der Pharmazie (Weinheim, Germany) (2000), 333(10), 323-328.
In addition, the following compounds with fungicidal activity were known in Bayer's patents WO2008003745 and WO2008003746, separately.

Although many piperazine and amide compounds were reported, it's still need to be researched and developed.